Hitherto, variable density spectacles which incorporate systems of rotatable light-polarizing lenses have been attended with serious problems of either undue mechanical complexity or oversimplification of structure to the extent of inefficaciousness.
Exemplary of prior art complexity in variable density spectacle structures are those of U.S. Pat. Nos. 1,879,793 and 2,380,481 wherein worm and segment gearing of the former and/or worm and ring gearing of the latter render such structures not only difficult and expensive to manufacture and unduly cumbersome, heavy and uncomfortable upon the face but unadaptable to face-forming for improved fitting and/or styling necessary for general public acceptance of such items as dress spectacles (sunglasses) rather than as necessary industrial or military eye protective devices.
Cases of oversimplicity rendering prior art variable density spectacles inefficacious are exemplified by U.S. Pat. Nos. 2,005,426 and 2,773,422 wherein there is a lack of means for coordinating the rotation of right and left eye spectacle lenses when adjusting the spectacles for continuously variable density effects. Detenting of the single lens rotations to preselected positions of use as disclosed in U.S. Pat. No. 2,773,422, for example, limits such use to preselected widely different degrees of density (light-transmission). On the other hand, freely independently rotatable single lenses according to U.S. Pat. No. 2,005,426 render the achievement of identical right and left eye lens densities extremely difficult and awkward. A smooth and continuous uniform transition in both right and left eyes from low to high density or vice versa is virtually impossible.
In connection with the aforementioned matter of publically acceptable aesthetics in variable density spectacle design, which is of extreme importance in the manufacture of dresswear items (e.g. sunglasses), U.S. Pat. Nos. 2,251,330 and 2,298,058 illustrate types of structure which are inadaptable to other than ordinary circular lenses. The flat circular lens has long been outmoted and is, with but few exceptions, publically unacceptable in dress spectacles. Additionally, frame front coquilling, i.e. bending or shaping according to the general transverse shape of a wearer's face for achieving wearing comfort and optimum fitting appearance is unattainable with structures of the aforesaid exemplary type. Such bending would interfere with useful operation of their lens rotating mechanisms.
The prior art inability or unadaptability to coquilling for face-fitting comfort and improved appearance is more clearly evident in frame front structures of the types shown in U.S. Pat. Nos. 2,813,459 and 3,371,979. While the adaptation of non-circular front lenses in these structures relieves, to some extent, the unattractiveness of old art circular lens shapes, the overall aesthetics of meniscus lenses and frame coquilling for fitting comfort necessary to achieve general public acceptance of variable density spectacles, especially as dresswear, is lacking.
Accordingly, it is a principal object of the present invention to provide such improvements in variable density spectacle construction as to overcome the aforementioned and corollary drawbacks of the prior art devices and wherewith aesthetically acceptable and mechanically dependable variable density dress spectacles may be simply, efficiently and economically produced.